Sohryuden (Legend of 4 kings)

The story is about the four Ryudo brothers, who live in modern-day Tokyo. They are descendants of the four Dragon Kings of Heaven and their generation, the 117th is the one in which the Dragon Kings' powers manifest. So in between turning into dragons when pissed off, they're on the run from the army, the police, and all sorts of other people who want them for their powers.